Transformer core



April 7, 1953 s. LARKIN 2,634,321

TRANSFORMER CORE Filed April 15, 1950 3 Sheets-Sheet l INVENTOR SAM LRK//V ATTORNEYS April 7, 1953 s. LARKIN 2,634,321

TRANSFORMER CORE Filed April 15, 1950 w 3 Sheets-Sheet 2 7 C INVENTOR SAM LAEK/A/ a BY 00,6%@

ATTORNEYS April 7, 1953 s. LARKIN 2,634,321

TRANSFORMER CORE Filed April 13, 1950 3 Sheets-Sheet C5 4 4 Za .la Z

INVENTOR 54M LAE/(IN BY 777009/ /gf/yK ATTORN EY Patented Apr. 7, 1953 TRANSFORMER CORE Sam Larkin, Pine Bluff, Ark., assignor to Larkin Lectro Products Corporation, Pine Bluff, Ark., a corporation of Arkansas Application April 13, 1950, Serial No. 155,728

1 Claim. 1

My invention relates to a new and improved transformer core and a new and improved transformer.

This invention relates to improvements in my application Serial No. 149,993, led in the U. S. Patent Oice on March 16, 1950, for Transformer and Method of Making the Same, which is now abandoned, and reference is made to the disclosure of said application lSerial No. 149,993, with the same force and eifect as if specically repeated herein.

The objects and advantages and features of this invention are disclosed in the annexed description and drawings.

Fig. l is a perspective view of two sets or stacks of laminations;

Fig. 2 is a section which shows the assembly of the stacks of laminations of Fig. 1, to make a single-phase core-type transformer. As in my said application Serial No. 149,993, this application also includes a shell-type transformer;

Fig. 3 is an end view of Fig. 2;

Fig. 4 is a perspective view of a set of laminations whose shape is different from that of the embodiment of Figs. 1-3 inclusive;

Fig. 5 is a top plan View which shows the assembly of three sets of the laminations of Fig. 4 with two yokes, in order to provide an improved three-phase transformer;

Fig. 6 is a section on the line 6 6 of Fig. 5;

Fig. 7 illustrates a modification of Fig. 5;

Fig. 8 is a section on the line 8 8 of Fig. 7;

Fig. 9 is an elevation which illustrates the interleaving of two sets of the laminations which are shown in Fig. 7;

Fig. 10 is a perspective View of each of the three sets of laminations shown in Fig. 7; and

Figs. 11-14 illustrate the assembly of the three sets of laminations of the last embodiment.

In my said application Serial No. 149,993, I have disclosed a method of making a stack of bent laminations, made of silicon steel or other material which is suitable for making the core of the transformer.

Figs. 1-3

This shows two stacks of laminations A and B. The laminations of stacks A and B are of the some width and thickness. Each lamination consists of a base-leg I and transverse legs 2 and 2a. Cin this embodiment, the base-legs I, 2 and 2a are Yiiat and rectangular, and the transverse legs 2 and 2a are perpendicular to the base legs I. For convenience, Fig. 1 shows the base-legs I horizontally disposed, and the transverse legs 2 and 2a vertically disposed.

(Ci. F- 356) Each lamination has transverse legs 2 and 2a of unequal length. For convenience, some of the transverse legs of stack A are designated by reference letters C, E, G, H, F and D. Likewise, some of the transverse legs of stack B are designated by reference letters Ca, Ea, Ka, Ha, Fa and Da.

The stacks A and B are temporarily releasably assembled by respective releasable clamps 3 and 3a. 4In each stack, the base-legs I abut each other. Likewise, the transverse legs 2 abut each other in each stack and the transverse legs 2a abut each other in each stack.

Each lamination of each stack has transverse legs 2 and 2a of unequal length. Thus, the rst or outermost lamination of stack A has a long transverse leg 2 and a short transverse leg 2a, respectively designated as C and D. The next or second lamination has a short transverse leg 2 and a long transverse leg 2a, respectively designated as E and F. The next or third lamination has a long transverse leg 2 and a short transverse leg 2a, respectively designated as G and H. All the long transverse legs of stacks A and B are of the same length, and all their short transverse legs are of the same length.

Long and short transverse legs alternate in each set 2 and 2a.

Similarly, the first or bottom lamination of stack B has a short transverse leg 2 and a long transverse leg 2a, designated as Ca and Da. The next or second lamination of stack B has a long transverse leg 2 and a short transverse leg 2a, designated as Ea and Fa. The next or third lamination of stack B has a short transverse leg 2 and a long transverse leg 2a, designated as Ka and Ha.

As located in Fig. 1, each long transverse leg lof one stack is vertically alined with a short transverse leg of the other stack.

Prior to assembling the core, the fastening means 3 and 3a are removed. A coil or coils T is Wound tightly on each set of base-legs I, in order to keep each stack assembled as shown in Fig. 1 and above described.

The stacks A and B and their coils `T are then assembled as shown in Fig. 2, to provide a coretype transformer. The straight and planar lateral edge of long leg C abuts the straight and planar lateral edge of short leg Ca.

Long leg Ea is interleaved with long legs C and G. The straight lateral edge of long leg Ea abuts the straight lateral edge of short leg E.

Similarly, short leg D abuts long leg Da and long leg F is interleaved with long legs Ha and 3 Da, and the edge of long leg F abuts the edge of short leg Fa.

Save for the outside long transverse legs C and Da, every long leg of one stack is interleaved with two long legs of the other to provide a lap joint. Each leg of one stack has edgewise abutment with a leg of the other stack to provide a butt joint.

The interleaving provides a series of close or tight lap joints, so that the assembled core has maximum permeability to the magnetic flux. In this respect, a lap joint is superior to a butt joint, because it is difficult to provide a tightly fitting butt joint. Also, the lap joints provide a frictional assembly between the stacks. Optionally, the frictional assembly may be supplemented by clamping means. In making the assembly, the coils I of the stacks are pressed against a spacer lic, which is made of pressed wood or other material which is insulating and which has minimum permeability to the magnetic flux.

Figs. 4-6

Fig. 4 shows a modied stack P. Three such stacks are used to form the yoke and legs of the core of a three-phase transformer. These three stacks P are identical. Their laminations are of equal width and thickness. Each lamination has a base-leg i and transverse legs 2 and 2a.

In this embodiment, the base-legs i are at and abut each other. The transverse and identical legs 2 and 2a are also ilat. In each set, the transverse legs 2 abut each other and the transverse legs 2c abut each other. Instead of being rectangular, the transverse legs 2 and 2a are rectangular up to the base-lines of their triangular tips, which have edges Pa and Pb. These edges Pa and Pb make an angle of 120 with each other. In each stack, all the edges Pa and Pb of each set of transverse legs 2 and 2c abut each other.

Coils Ta, Tb and Tc are wound tightly around the abutting base-legs I of the respective stacks P, thus holding said stacks assembled.

When the three stacks P are assembled as shown in Fig. 5, they abut each other tightly at the edges of the triangular tips of the respective sets of transverselegs 2 and 2a. The assembled transverse legs :2 thus form one part of the yoke of the transformer, and the assembled transverse legs 2a form the other part of said yoke.

Each assembled set of transverse legs 2 and 2a is maintained in clamped relation by a respective pair of clamping plates Q and lla. These clamping plates have alined perforations, through which the Shanks of bolts 5 extend. Clamping nuts 6 and 6a maintain each set of clamping plates i and 5 in rm clamping engagement with the respective set of transverse legs 2 or 2a. This construction provides an improved threephase transformer, which can be made and assembled at low cost. The bolts 5 clear the legs 2 and 2a.

Figs. 7-14 In this embodiment I use three sets of stacks X, Y and Z which are shown in perspective view in Fig. l0. The stack Y has transverse legs Ya and Yb. The stack Z has transverse legs Za and Zb. The stack X has transverse legs Xa and Xb. In each or" the stacks X, Y, and Z, the base legs abut each other, and the respective sets of transverse legs abut each other. The laminations of each stack are of the same width and their base legs and transverse legs are planar. In each stack X, Y and Z, the transverse legs are perpendicular to the base legs, in this embodiment.

Each transverse leg has a triangular tip, whose edges make an angle of The set X has transverse legs Xa which are of identical size. The transverse legs Xb are alternately of different lengths as shown in Fig. l0. The transverse legs Ya and Yb are alternately of different lengths as shown in Fig. 10. |Ihus, in the outermost or top lamination of the set Y, there is a long transverse leg Ya and a short transverse leg Ya. In the stack Z, the transverse legs Zb are identical and the transverse legs Za are of alternate different lengths. Since these features are clearly shown in Fig. l0, further description is unnecessary.

Fig. ll illustrates the assembly oi the respective transverse legs Xa, Ya and Za at the level il of Fig. 9. rEhe lines 2i), 2l and 22 respectively indicate the axes of the respective legs Ya, Za and Xa at said level il, and the peint 23 is the intersection of said three axesr 23, 2i and 22. At the level il, there is a long transverse leg Ya and a short transverse leg Za. The respective legs Xa and Za have spaced edges which are parallel to each other and which are parallel to 4the axis 20. The other edges of the transverse legs Xa and Za abut parts of the edges Pa and Pb of the long transverse leg Ya.

Fig. 12 illustrates the assembly oi the respective transverse legs Xa, Ya and Za at the level I2 of Fig. 9. Fig. 12 shows a short transverse leg Ya and a long transverse leg Za. The legs Xa and Za have edges which are parallel to axis 2S and which partially abut each other and which are oiset from the axis 26.

Fig. I3 illustrates the assembly or" the transverse legs at the level I3 of Fig. 9. This shows a short transverse leg Yb and a long transverse leg Xb. Since Fig 13 accurately shows the assembly at the level i3, a detailed description is not necessary.

Similarly, Fig. 14 shows the assembly of the three respective transverse legs at the level Iii. This shows a long transverse leg Yb and a short transverse leg Xb.

The above is suiiicient to illustrate the assembly of the three transverse legs at each level of the complete embodiment which is shown in Figs. 7 and 8.

I thus produce an eiective interleaving of the transverse legs, thus producing close or tight lap joints which provide yoke members of maximum permeability to the magnetic flux.

In said application Serial No. 149,993, filed March 16th, 1950, I have disclosed that each lamination is shaped individually to the desired nal shape 4from an original flat blank by gliding or wiping pressure, and to provide each lamination with rounded walls of small radius oi curvature at the junctions between the base legs and the transverse legs, and that said walls have the same large curvature at said junctions in all the laminations of a stack. By using such wiping pressure,'no direct bending pressure which would compress the laminations is exerted, save at said junctions. Each lamination therefore substantially retains the original thickness of the original blank, which is substantially of uniform thickness.

For convenience, the stacks X, Y, Z are respectively designated as the iirst and second and third stacks. The sets of transverse legs Xa, Xb, Za, Zb, Ya, Yb are respectively designated as the rst, second, third, fourth, fifth and sixth sets.

I have described preferred embodiments of my invention but numerous changes, omissions and additions can be made without departing from its scope.

I claim:

A core for a three-phase transformer, said core consisting of first and second and third elements, each said element being a stack of laminations which respectively have base legs which have transverse legs at the respective ends thereof, each transverse leg having a tip whose edges meet at an angle of 120, said laminations respectively having rounded walls at the junctions between said base legs and said transverse legs, said walls having substantially the same curvature, said base legs abutting each other, the respective side edges of the laminations of each element being in respective alinement, the transverse legs at the respective ends of the base legs of said first element abutting each other to form first and second sets of transverse legs, the transverse legs at the respective ends of the base legs of said second element abutting each other to form third and fourth sets of transverse legs, the transverse legs at the respective ends of the base legs of said third element abutting each other to form fth and sixth sets of transverse legs, the rounded walls at the junctions of the transverse legs of each set abutting each other, the legs of the second, third, fth and sixth sets being respectively alternately of a rst short length and a second long length, the legs of the rst and fourth sets being all of the first length, the rst and third and fifth sets being at one end of the base legs of the assembled elements, the second and fourth and sixth sets being at the other end of the base legs of the assembled elements, the respective tip edges of each long leg of the fifth set abutting respective tip edges of a leg of the first set and a short leg of the third set which are spaced from each other, one tip edge of each short leg oi' the fifth set abutting one tip edge of a long leg of the third set whose other tip edge abuts one tip edge of a leg of the first set which is spaced from said short leg of the fifth set, one tip edge of each short leg of the sixth set abutting one tip edge of a long leg of the second set whose other tip edge abuts one tip edge of a leg of the fourth set which is spaced from said short leg of the sixth set, the respective tip edges of each long leg of the sixth set abutting respective tip edges of a leg of the fourth set and a short leg of the second set which are spaced from each other.

SAM LARKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 400,862 Lowrie et al Apr. 2, 1889 2,367,927 Chubb Jan. 23, 1945 2,380,300 Gaston July 10, 1945 2,456,459 Somerville Dec. 14, 1948 2,456,461 Dunn Dec. 14, 1948 2,477,350 Somerville July 26, 1949 

